Several inspection techniques are employed to scan, detect, assess and otherwise analyze the shape and surface characteristics of a solid object. Those techniques and in particular optical inspection techniques often require specialized preparation of a surface, or surfaces, of a solid object to be inspected. A number of factors can affect the optical inspection results, namely roughness, reflectivity, coloration, porosity and physical continuity. Not all those factors are essential in non-optical inspection methods.
By way of example, optical inspection techniques such as Shadow and Projection Moir e, Laser Shearography, Diffracto Sight, Back-Lighted Grid and Laser Beam Scanning require highlighting of the surface to be inspected to obtain its suitable reflectivity. It is known to modify surfaces to be inspected with specific liquid, paint or powder highlighters. This approach has the following drawbacks:
the highlighters are often solvent based and thus not environmentally neutral; PA1 application problems (liquid-surface wetting, distribution and evaporation, non-uniformity of coverage); PA1 removal problems (highlighters can be absorbed into the surface which may require additional removal processes and result in contaminated waste products); PA1 evaporation rate of some highlighters restricts the duration of the inspection and lowers inspection repeatability; PA1 incompatibility with inspected material (adverse effect on the inspected surface); PA1 surface coloration read-through (non-uniform surface coloration may affect the inspection results); PA1 porous materials cannot be inspected with liquid highlighters; PA1 temperature dependence--evaporation of some highlighters; PA1 surface contaminants may affect highlighting quality; PA1 difficulty in controlling the surface roughness; PA1 non-reusability. PA1 a) applying a layer of a solid, deformable film to at least a part of the surface to be inspected, and PA1 b) bringing the layer and the surface or the part thereof into a controlled contiguous relationship. PA1 a sheet of a solid, deformable film, PA1 holding means for holding the sheet against a selected solid surface to be inspected, and PA1 means for forcing the sheet against the surface (or a part thereof) to achieve a controlled contiguous relationship therebetween.